Of course you can sell RepRaps. And there already are some resellers that offer complete printers and DIY kits. Some companies made there own variants of RepRap-printers and sell them.

Open Hardware means, that no one claims to have the exclusive rights. This reduces the profit one can make with RepRap-technology, and this is by intention. You may sell parts and complete printers but will only be paid for the reselling process, not for any 3D-printing know-how, because that's not owned by you.
The idea behind RepRap is to make 3D-printing available to everybody. So you will not become rich with selling RepRap-parts, but you will be part of spreading the technology to more people, getting reward for that.

As long as you respect this fact, you may sell RepRap-printers and parts as requested.

To be honest: The profit margin will be limited and that's the cause for the limited number of companies, running exclusively on this business. You should enrich your business model with additional ideas, e.g. according to and accompanied with RepRap 3D printing, filament a.s.o.