As opposed to most commercial and even non-commercial projects, Ronja doesn't try to raise artificial barriers preventing people from exploiting the intellectual property generated by development for their own profit.
The most obvious way how one could immediately start using the Ronja intellectual property to make profit is selling DIY kits for end users. It doesn't require almost any investment, because everything is published in a fully prepared state. Even some immediate customer interest can be expected, as people often ask on the mailing list why noone is manufacturing DIY kits yet.
This ready availability is a side effect of Ronja's User Controlled Technology policy. We believe that artificially created barriers preventing one from using another's intellectual property carry significant overheads for the society. Basically one invents a wheel and then tries to sell it overpriced. Another one, to avoid IP infringement or because the IP is kept secret, has to invent wheel twice. Instead of pushing the mankind towards brighter future, inventors have to waste time on an artificially created problem this way.
Obvious argument against this is how the inventor gets paid for his invention. The method we developed to counteract this problem is simple - design something and ask people for donations. When the donations cover the cost of time and material to develop it, release it under a free licence (GNU FDL). For more detailed discussion of this approach, see Ronja Project Sustainability Philosophy.
The most wanted parts that are easiest to sell are: