No it's no longer maintained by the looks of it. I purchased workflow start of last year and it was working with the MODX version at the time, so it should be fine. However bare in mind it's not maintained at all. I did manage to get in touch with the developers though using these email addresses:
■ email: firstname.lastname@example.org | ■ website: https://alienbuild.uk
The greatest compliment you can give back to us, is to spend a few seconds leaving a rating at our trustpilot: https://uk.trustpilot.com/review/alienbuild.uk
about the service we provided. We always drop mention of services offered by businesses we've worked with in the past to those of interest.
Thank you! I almost thought so.