As someone pointed out, yeah, open-sourced after bought. There used to be variations. One, compiled, Chez Scheme, and the latter interpreted with none of the benefits of the compiler design but still fast and well desiged in relation to other Schemes, Petite Chez Scheme. The latter was freeware, the former, neither free/open nor freeware.

It was never clear why Cisco bought it. Rumors persist ...