To get some ideas on licensing, perhaps you can read the part of pre-existing forum software most people skip: the licensing agreement.
Mainly, just go find some publically available forums.
If I recall correctly, this "phorum" is open-source/free.
You might want to (if you haven't already) take a look at sourceforge.com and look for existing forums, especially those made with PHP.
You could get some ideas for improving your own system, and get some ideas on licensing.
A few things to consider when pondering the commercial feasability of your product:
The current market saturation. There are alot of forums out there, and to get customers you have to prove that yours is BETTER, for whatever reason.
Mass-market appeal. Can you get a site like this one to use your forum system? If you sell it, you may want to give away licenses to major sites as a promotional idea.
Of course in comes the old debate of Open-source freebie vs Commerial product.
One thing to think about, is what would be more valuable to you, in the long-term. A publically used and accepted piece of software, which allows you to showcase your abilitys and prove that not only can you finish a job, but you are in fact a good programmer.
Would the job opportunitys be worth more to you (in time, security, and/or monetary funds) than selling your forum?
Another problem with selling your forum, is of course the fact that you really have no way of protecting your source code from hitting the mass-market (via "warez", couriers, etc).
Your only protection would be your lawyer, and what he could do to take legal action against people you find using unlicensed versions of your software.
But then comes the fact that people can rip off your code.
When it comes down to it, your just as vulnerable when you sell it as you are when you give it away.
If someone wants to take your code, strip it of commenting, rename the variables, and slightly re-arrange the code flow, what can you really do about it?
Even a product that took a year to build can be ripped off in a matter of weeks.
This is just "acceptable loss". It doesn't happen too horribly often, and as long as you come off as verious serious about protecting your property rights, you should be fine.
Now the real question is, why have you created your program? (for all intensive purposes, legally and ethically, "code" is just as much your property if it was written in proprietary VisualBasic as if you wrote it in open-source PHP)
In my ever-so humble opinion, people only write software for 3 reason.
To make money.
To stroke their ego/impress people.
As a learning experiance/fun.
If your just going the ego/impress or experiance/fun route, go open-source. It's the best way to make people "know" you and your work.
Now, let's say your out to make money (which is more complicated).
3 ways to make money off your work, really.
Sell it.
Improve it as free software, then sell it.
Pad your resume with it and get paid to do something else. (thus selling yourself...not like that, sicko)
First you can just go with what you said and sell it as a commercial product.
Allow people to pay for it, then allow them to modify it however they want, as long as they don't distribute it in any way beyond the restrictions of their license.
You can release it as open-source free software and build it up. Kill the bugs, pack on the features, but don't get it into perfect working order in your public release.
Get up to, let's say, version 3, improve the software to where you can't even think of a way to make it better, declare it "Platinum Version 5", or whatever, and sell it!
Keep the old version as free and openly distributed, get a good demo of the commercial one working, and that should work.
No matter what route, you can make money if you want to work at it. Just some ways aren't 100% direct of going about it.
The only thing you have to worry about when your going commercial, is the facts are sales will probably be nearly non-existant.
You'll pretty much be unable to really sell your forum untill you've had it around for multiple months and are up to v2-3.
It takes time to get market penetration, consumer confidence, product reliability, etc etc.
If your not going to have another company market your product (in exchange for cash, of course), it's going to be a whole crap load of work.
And it's not the work most programmers like.
Just one of the many things to be aware of...money sure does make things complicated, doesn't it? 😉
In any case, good luck with your product! By completing it you'll beat at very least 10-1 odds. (usually the projects started to projects complete ratio is even bigger)
One possibility you may also look into is http://www.asynchrony.com/welcome.jsp
One of the companys that will help you with the marketing and production in exchange for a suprisingly small cut.
