The post titled 'Official and Unofficial "Fixes"' in the above thread on the Spybot site makes it clear that 1.3.1TX is unauthorised and unsupported and that it was withdrawn. When referring to this version and other betas the post says, "We strongly advise you not to use these versions". The latest fully-released version is still 1.3 and the latest beta is 1.4.2. The thread gives instructions for installing the latter.
If you are happy, fair enough. However, it might not work for everyone. The developer is quoted in one post in another thread as saying that TX mght cause problems with some updates. Who knows what support you would need? I'm just quoting the Spybot forum.
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