To be 100% correct, no. We are soon including a vendorField which was requested by our community. It was one of the first feature requests ever and lately we progressed enough so we can implement useful community requests.

Here you can see the progress on that feature: https://github.com/LiskHQ/lisk/pull/470

Currently planned for Lisk v1.0.0: https://github.com/LiskHQ/lisk/projects/6



So with that vendorField you can implement things on top of Lisk, without our SDK. I.e. what people are building on top of Bitcoin or Nxt, e.g. Counterparty, Tether, notaries, one-sides bridges and so on. For some use-cases other features might have to be implemented.

However, of course this is not our intention. We intend developers use the future Lisk SDK, however it's still an option. I'd like to clarify that this is nothing new. Bitcoin or Nxt have it since years, and it's being used quite a lot.