@User the PDK started as a Virtuoso PDK and was transformed to it's current state. Therefore, it can be transformed back, it just takes work. If you have some kind of organisation behind you (university/company) you can sign the NDA with Skywater and get the Virtuoso PDK. But, if you want to submit to the shuttle the design has to be open source. Then your organisation needs be sure the license agreements they signed aren't violated by revealing all sources.