My context: I live in the Netherlands and I have written Apache 2 licensed software that is used globally.
I have created a UDF (User Defined Function) for a piece of closed source software (https://github.com/nielsbasjes/yauaa/blob/master/udfs/platfora/src/main/java/nl/basjes/parse/useragent/platfora/AbstractAnalyzeUserAgent.java).
The (Java) interface needed to build this software is provided by this company to all of their customers as part of the tool installation.
The interface is trivial and does not contain any code, it is just a single, very simple interface. The online documentation (https://documentation.platfora.com/webdocs/#reference/expression_language/udf/write_udf_java_program.html) gives enough information to recreate this interface from scratch.
They have indicated that they do not want to publish this interface to maven central (in this case simply because the product is end of life).
I would like that anyone can build my software from source without having to download and install extra stuff (i.e. this interface).
To what extend am I legally allowed to recreate this interface from their documentation and make it part of my source tree?