There is a free but limited version. It's the trial. no record limit, just a 30 day time limit. You can learn a heck of a lot about FileMaker in 30 days and get over quite a few curves.
If you're looking for developer training, you're going to want to invest in a copy of FMP advanced anyways pretty early in your career. Given that Devcon gives you a free copy of FMPA for attending, you might want to look into attending and taking training there.
Remember that the majority of licensing sales FileMaker makes is to client/users, not developers. So I wouldn't think it would make business sense to have to build a special version of FM just for an extended developer trial.
30 days is not enoough time if you have a full time job too. A limited free version allows someone to tinker in their spare time a few hours here, a few hours there.
More significntly, for some users the free version would be sufficient -- they are with data sets a bit too large for a spreadsheet, but making the transision to a database isn't yet in the cards. They try it, they get cofrable with it. Their project grows. They become customers. Meanwhile, you have a bunch of people who use it, and talk about it.
A free version allows use in high school computer labs. And, yes, I know that FM gives educational discounts. What you don't know is how constrained high school budgets are. I ran a high school computer lab on a budget of 6000/year. That budget had to provide for all equipment, all repairs, all software, and our bandwidth to the world. $179/seat for software that would be used for half a semister for one grade is not going to happen.
I feel your pain, I used to work for a library with a limited tech budget, short of monitors catching on fire (which they did), nothing was ever replaced.
FileMaker Inc. is, first and foremost, a business. So to do as you suggest, they would need to see a path to a large payoff in the investment of "giving away" a light-version of FM. I just don't see that as happening, but I'm not necessarily a "bigger business picture" kind of guy. This is exactly what happened with FMGo. Early on it was a pay-to-play app, then when FM12 came out, boom, free app. The flipside of that is connection packs on FMS13 now though.
FileMaker did offer a training license package for authorized trainers. I'm not sure how that's changed with the FM13 licensing shift, but it might not hurt to call your local licensing rep and see what's possible.