'[Old versions] will be open source' would, I think, also be a fair description. Right now it's source available proprietary freeware; in three and a half years

'[Old versions] will be open source' would, I think, also be a fair description. Right now it's source available proprietary freeware; in three and a half years it (specifically, the now-current version) will be open source. For this reason, I think the Business Source License (BSL) (with an Open Source Change License) is less nefarious than the Server Side Public License (SSPL).