No so, having looked at other successful software based kickstarter projects - it is quite feasible to have recognition based rewards.
We can easily add a "Medal" or something underneath a user name indicating they contributed!
It would only be a reward for forum members, but I've seen other forums use that type of graphic for various things, so it's one of many "intangible" rewards that could be offered.
Hard coding a list of names of contributors in a splash screen or elsewhere in MB3D is another idea, but if it's open source that may not work.
But the point is that intangible rewards can be done and there are many options for them.