Do you mean legally or how long will it remain functional?

Since it is open source and have downloaded the package, nobody can restrict using it in case oxwall discontiuned. 

I mean how long would it work with your server. I heard that when the version of your server is updated it isn't compatible with older versions of php and other software

Of course you need to do some tweaking in the software to make it compatible with the server configuration. Some are easy some requires a lot of customization as some syntax, methods and other stuff become deprecated. We can't tell you for sure for how long it work 

Is it me or you have asked this question like 3 times already? 

i am just worried this software won't work in the future with my server

Our requirements can change easily and you have to configure your server accordingly. 

Austin do you know something we dont?  Oxwall is not going anywhere sir.   

Also regardless of the software you choose, change is a part of the process just as change is a part of life.  It does not matter what you choose you cannot avoid it. Just dive right in, have some fun and enjoy creating your social site.  :)

Dave +1