When you first meet with the community group, be open and honest about your level of commitment (taking into account your professional and personal commitments). If you think that it’s too much of a commitment then you are entitled to withdraw at this stage.
However, once you agree to proceed with the project, the community group will be relying on you and it costs them time and money if you pull out of the project.
If you need to withdraw once the project is already underway, ask your colleagues if they are interested in helping out and talk to GoodCompany to see if they can help find someone else. The most important thing is to communicate with the community group and/or GoodCompany about your situation.
An unsuccessful/incomplete volunteer project costs the charity valuable time and resources.