There's no such thing as "semi-open source" It either is open source, or it isn't. The nature of open source makes it so that everything built upon it must be open source according to most of the open source licenses. The idea you're proposing is very popular and used all the time by big successful companies. See Redhat, Atlassian, vTiger, SugarCRM, WordPress (Automattic). The key is offering value on top of the open source free/community package. The value for an enterprise would be your service and expertise in maximizing the software, professional support, or customizations for them, or even hosting it for them. The upsides of doing it via open source is that the small companies that won't pay to license or service fees will customize some of it and hopefully contribute back to the software which will make it stronger for everybody. And as they grow they might eventually need your services or paid offerings.

You have 2 recommended options. Use single installations for each /1, /2, /3 and a main installation as the home page. Or just use the one database. As your site grows, if you need to add more resources to the database, you'll add extra database servers to handle the load but the data will still be in one database, you'll just use load-balancing technology to distribute the load.

There's a lot to consider. For a lead generation deal to be fair to both parties though, a fee for *qualified* leads needs to be in place whether the lead converts or not. Notice there's a big distinction between "qualified" and "quality." If someone sends you 50 *qualified* leads and you only convert 1 or less, the problem might be with the conversion part and the lead producer shouldn't be held responsible for that. What you should do is test out 2 or 3 lead generation methods. 1 of them being the other speech pathologist, measure out the conversion rates and then establish a base price. Then monitor the quality of the leads. 45-90 days is a good time-frame to make judgments, comparisons and adjustments. But what is not equitable to the referring party is to say I will only pay you if your lead converts, because without knowing all the components of the process, the same leads that didn't convert with you might convert really well for a competing business. A fixed price with a bonus structure would be good to make sure the receiving party is going a good job at actually converting the lead and for the referring party to be incentivized to send leads.

I don't suggest any affiliate networks as a tool to "scale quickly" that is not the purpose of affiliate marketing or even these networks and chances are that if you don't have the relationships in place already, you will fail at this attempt. You need to establish the relationships first... and that is not "scalable" you have to put in the work to build key influencers as brand ambassadors and then move into affiliate marketing.

The actual process of this is based on the company policy. I deal with some companies that will not mix the two types of income at all, while other companies treat all of it as earnings. As far as the legality of it when you receive the funds, it is totally up to the applicable tax laws for your particular case. The best way to clear this up would be to talk to an accountant specializing in affiliates.

It is very important for branding and authority. But it is more important for you to have it than your competitors. If you can get it, then get it. If you can't, then your app or service or offering will need to be amazing to overcome branding, authority and trust issues. The reason the giants have the .com is because it is necessary to demonstrate authority, longevity and trust. Good dot com names are also indicative of good business sense. Planning, creative inclination and or the ability to buy a good domain $2000 to $10000 or more say a lot about your business.

Dan is right, that's where you start. Here's a guided answer if it helps. https://www.youtube.com/watch?v=-oijCV-Klao

You can't think of buying traffic as an expensive proposition. All in all, organic "free" traffic is always more expensive in the long run. Properly targeted paid traffic is the best investment you'll make. As for ways to get organic traffic, create demos on how people can use your software to solve their problems. Use a blog and youtube videos to demonstrate the capabilities of the software by solving a specific issue. Do not just make a demo of the software to show the features, it must show a solution. Participate in social media and answer questions for the consumers. For affiliates, offer bonuses and special offers to join your program and nurture the affiliates. Find them by name and approach them personally to review the software and use it. You also should give it to the affiliates you want to promote your product, for free. I'd be happy to help you over the phone with this when you are ready.

You need quite a bit of "extra" stuff to make your plan work. You're on the right path, but I think you're missing a few components. I would always try to capture the lead and then get them to the action/sale/download/etc -- This way you have a chance to warm them up and promote the offer a couple times. Specifically the landing page you send them with that domain is a little confusing and seems overcrowded with stuff. I would always send them to my own landing page (easy to make). Collect the lead (easy to do), then send them to your offers. Overtime, keep a good relationship, you can market them other similar products. In this specific case, your ad may have had the wrong call to action or a mismatch on your ad vs the landing page. can't tell without looking at your ad. And without a more in depth discussion. I know there's a lot more to cover, but these could be some things to think about.