It is tempting to think that the reason open source software works, is because it is free. Linux, Apache, Nginx, android are all open source software and they make the world go around. It helps that they cost nothing to get, but the reason they are so successful is because they are amazing pieces of software.
Github, is filled with projects no one wants to download. For the record I didn't check the numbers but I do believe github is the biggest source of free software of our generation. I don't know if SourceForge is actively maintained and only rarely stumble upon it.
If Apache was a paid application, I would still pay for it. I need it to do my work and it takes so much of the hurdle of creating a web server from scratch out of the equation. If PHP wasn't free, there would be less websites but it will still be amazing and worth paying for.
The free part of software allows for massive download rate but the retention rate is dictated by its awesome factor. Just take a look at Google Play versus iTunes. Android developers complain of not making a lot of money. The reason is because of the retention rate. Everyone gets excited by the download rate, but only the developer sobs under the high deletion rate.
That's what happens when your killer feature is Being free.
Linux runs the most webservers today not because it is free but because of the freedom it gives. At least before Microsoft was becoming softer in its licenses, you couldn't spin VMs as freely as you wanted with Windows. You had to have a license with each instance. And that was a huge monetary investment.
With Linux, shared hosting companies have the freedom to have as much instances as they could physically have. Anyone can download Linux and instal a prototype of their application without having to make a trip to the accounting department. This is the freedom that Linux allows.
When you make your tools open source, think about the statement you are making. You are giving freedom to your users and freedom is a very expensive commitment. You are not asking to download a crappy app for free. You are telling them that you have created a tool that will make their life easier.
Open source is not a lesser app. It is as amazing if not better then the paid counterparts and will be competing as long as the software is relevant. One application that inspires me is Blender 3d. No, getting half a million downloads a month is not what impresses me the most. What matters to me is that it is competing with the big names that costs thousands of dollars. Blender is a single program that offers solutions to every aspects of the computer graphics industry. And it is free.
Today, Blender's only limitation is the creative mind of its users. And that what makes it an amazing piece of software, not the millions of downloads it gets. Just like the Apps market, I'm sure that out of the 500k downloads it gets a month only very few use it regularly.
Open source is not a plea to download a software for free. It is a plea to download free software. Subtle but big difference. When software cost zero dollars, you should be worried you are the product. When the software is free, it extends that freedom to you by giving you full creative control.
Open source is not a trick to get people to download your app because it is free. You are held to the same standards as paid software.
In other words open source is not a charity. When you create a free software and share it on github, remember to put all your effort into it and make something worth sharing. While you are at it, don't forget to get paid for it.