HT-2021-000363 - [2025] EWHC 532 (TCC)

AMBLIST is a batch utility provided with z/OS that can provide information about a load module. Such information includes the parameters and options used when creating the load module, a list of the CSECTs in the load module and the assembler used to create the load module. It can be used to print a formatted listing of the contents of the load module, including the object code and EBCDIC text, but it cannot disassemble the object code.

On 28 January 2016 Mr Taylor of LzLabs opened DR-1502, requesting Winsopia to use a tool such as AMBLIST on CICS stub modules that form part of the CICS Transaction Server to identify the entry points and their corresponding offsets used in COBOL, PL/I and Assembler programs. Four CICS stubs were analysed by Winsopia. Mr Lynch stated in his witness statements that he would have run AMBLIST on the IBM CSECTs to respond to the DR.

The experts agree that Winsopia used AMBLIST to derive information about the size of the CICS stubs, the entry points of the stubs, their offsets within the stub modules, the addressing mode specified and eyecatchers associated with the stubs. From this information, Winsopia created its own replacement CICS stubs, which were included in the load modules sent to LzLabs.

IBM’s case is that Winsopia analysed the CICS stubs with AMBLIST in order to create replacements for these stubs, amounting to reverse engineering a component part of the CICS Transaction Server.

The defendants’ case is that the CICS stubs are not ICA Programs, there was no reverse engineering and Winsopia’s acts fell within the scope of its rights under Article 5(3) of the Software Directive.

The issues in dispute are:

The IBM CICS stubs were generated by, and form component parts of, the CICS Transaction Server. The defendants submit that they are not ICA Programs because they are not self-contained components of CICS and are interfaces containing none of the commercially valuable processing of CICS. I reject that argument. The CICS stubs are an essential part of the CICS Transaction Server process, without which the CICS services would not be called at runtime. For the reasons set out above, I accept that they fall within the definition of ICA Programs within the meaning of the ICA.

Although AMBLIST is available as a debugging tool, Winsopia did not use it for such purpose. It was used to expose the names, lengths and offsets of the IBM CSECTs in the load modules, so that Winsopia could provide placeholders for LzLabs to insert equivalent replacement CICS stubs. This amounted to reverse engineering of the CICS Transaction Server v5.

The defendants submit that Winsopia’s activities fell within Article 5(3) of the Software Directive on the ground that Winsopia was entitled to investigate interface information relating to the CICS stubs. I reject that argument. There is no suggestion that Winsopia used AMBLIST for the purpose it was designed, namely, debugging. The information produced about the load modules enabled Winsopia to gain an understanding as to the sequence and combination of code used by the CICS Transaction Server to implement the CICS services. That concerned expression of the program, rather than its functioning.

In summary on this issue: