Please note that the SQL Anywhere software that was installed with SAP/Sybase PowerBuilder is a Developer edition. It cannot be used with deployed applications. The only deployment license that ever was included with PowerBuilder was the Runtime Edition. It was name rtengX.dll where X is the major version of SQL Anywhere. The Runtime Edition was deprecated some time ago.
You can continue to use SQL Anywhere 12 (albeit it has been end of maintenance for some time) subject to your licensing. For example, you may continue to use the SQL Anywhere 12 Developer Edition with PowerBuilder 2017 for development work.
If you simply want to continue to use SQL Anywhere 12, access to historical software updates remain on the SAP Software Downloads site under Archived Products. Updates can be applied to all Editions including an active Trial Edition.
If you want to move to a newer Developer edition, please visit SQL Anywhere Developer Edition. This edition is a full feature product except that it cannot be used in production. It will have features and capabilities that may not be available is all production licenses. For example, High Available is not available in the Workplace license but is available in the Developer Edition.
There is also a limited time Trial Edition. The Trial Edition is no longer made available as a separate download. If you install without a registration key (you will be supplied a key for the Developer Edition), the software defaults to the Trial Edition which I believe is a 60 day period.