1). Code freely scrutinized by anybody means that many bugs and security vulnerabilities are corrected fast
2). Code can easily be modified to do whatever you need it to do, specifically. If you aren't a coder, you can probably find a forum site which will tell you exactly how to make it do what you want.
3). Support forums are often active including the person or persons who actually wrote or maintain the software. Therefore, you get an authoritative answer from the person who knows best.
4). Open source software can be modified, then re-distributed. So, you can even charge for your changes and support for those willing to pay for it. Of course, you have to continue providing all source code including your changes and cannot further restrict anybodies ability to use it.
5). Packages are often maintained as long as somebody has a need for it. And if the package is still relevant and somebody is passionate...development can continue. This differs from closed-source where once a company decides to no longer support or provide updates..you are simply out of luck.