I will answer my question with my conclusions:
-NWitsml.org - open source access, read-only access to witsml servers. Compatibility 1.2 to 1.4. Based on java code from a Jwitsml project.
-Standards DevKit - read and write access to witsml-servers 1.3.1 and 1.4.1. Makes "dumb" serialization / deserialization of requests and witsml documents, i.e. Tracking the state or understanding what the request contains, so the operator must know the specification well enough to create the right request. Open source.
-Setiri.Witsml SDK - read and write access to witsml servers version 1.3.1 (compatibility 1.4.1 in operation). Entities track their state and include a lot of witsml knowledge, so the user does not need to be a guru, thus a more developed / mature product. Developer Place License.
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