Make sure you have set up your server correctly before you start developing. Read the README.md, specifically the Server Requirements section. We recommend DigitalOcean for your server. Install Ubuntu Linux 14.04 on, preferably, a 1 GB droplet. (Note: the next version should work better with Ubuntu 16.04). If you sign up with our link, you'll get a $10 credit.
If you want to pay someone to do the development for you, you have two choices: you can hire us or you can hire someone else. If you want to hire us, feel free to contact us. You can always hire someone else as well. If you do, just point them at these resources.
After you or someone else has made changes to OSPOS, consider creating a new pull request at the official OSPOS repository. That way your changes won't be overwritten if you update the software in the future. Plus, you're giving back to the OSPOS community.