The NanGate45 Open Cell Library is available under the Apache2.0 license from Silicon Integration Initiative (Si2). It is based on FreePDK45 from North Carolina State University. [FreePDK45 Link]
As the FreePDK45/NanGate45 enablement does not have memory generators, we use the bsg_fakeram memory generator available in the bsg_fakeram GitHub repo.
With this combined enablement, testcases with SRAMs can be synthesized, placed and routed using both proprietary (commercial) tools such as Cadence Genus/Innovus, and open-source tools such as OpenROAD.
The ./lef directory contains the technology, standard cell and macro lef files, the ./lib directory contains the standard cell and macro liberty files and the ./qrc directory contains the qrc technology file.