I agree with Damion below, cashless or net-issue exercise options and notes can be used, but you have to determine fair market value of the stock. One of the biggest issues for the employee also has to do with their own tax consequences. I don't want to get into all the specifics as those depend upon all kinds of variables, but employees often feel they are being cheated by not being able to actually get the stock and the option expiring. If they do exercise, there can often be tax consequences to them that they don't realize and may not want to exercise if they company doesn't have a way for them to liquidate the stock they end up with.
There are alternatives to the traditional stock option plans, such as SAR, phantom stock, ESOP, restricted stock purchase plans, and other plans that may provide incentives, but there are usually restrictions built in to those as well.
Unless you have cash to pay bonuses or other comp in place of options or you give a direct stock grant, those 90 day restrictions are pretty common and the employees need to understand that going in. Once the employee realizes the tax issues to them and their likelihood of being able to sell the stock down the road, they may reconsider just how valuable those options may be. I have seen clients go public with former employees holding stock options or warrants allowing several years to exercise their option and never doing so because even with a public company, the tax implications and low stock price do not make it worth doing so.
Thanks for asking me to answer, but I can't really give an answer either. Any "crowdfunding" involves securities, finance, and corporate law, but is just a new name to what startups have been trying to do for years. The only change has been the economy resulting in new legislation and an online push for startup funding. Businesses used to try to do the same thing with small amounts of cash from lots of investors, but regulations were put in place to protect investors and the market.
It will take some time before anyone really knows the full extent of new SEC rules and other changes, but any securities lawyer who deals with start-ups, venture capital, angel investors, emerging growth, entrepreneurs, and related issues have to stay up on this topic. My take is that no lawyer feels this is such a huge area that they would try to become an expert. I would rather wait until the hype dies down on this to see what happens as this trend may not end up being as great an opportunity after regulatory agencies crack down or shareholder/investor lawsuits start kicking in. The problem of minority shareholders and their rights has been a major area of concern for years with small and growing companies and this creates the potential for even more of those issues to arise with so many investors.