Greenbone OS: Transition to time-based release schedule

In the year 2019 Greenbone will switch to a new release scheme for Greenbone OS: the time-based release schedule.

Basically it means we will have fixed and reliable release dates. More specifically, it will be the very same dates for each year. Everyone can base internal planning on this schedule: Greenbone customers, partners and of course the Greenbone development teams.

These two release dates will be April 30th (in 2019: GOS 5.0 for ENTRY/SME) and October 31st (in 2019: GOS 6.0). 2019 is the transitional year where GOS 5 will be released in the traditional 2-step split for ENTRY/SME and MIDRANGE/ENTERPRISE/SENSOR. But GOS 6.0 will be released already according to the new scheme and in a single step for all GSM appliances. In 2020 the new scheme fully applies.

The new scheme is based on hard deadlines for new features, new GSM types and new hardware.
If a feature does not make it into a release, it will be prepared for the follow-up release. The cycle of two major releases per year dramatically increases the pace for getting innovations to the users.

The lifecycle of the releases allows to either jump on the next major release every 6 month (the innovation cycle) or to have a 3 month period for migrating across 2 generations every 12 months (the conservative cycle). For the latter, there are two time windows of 3 month per year to choose: May/June/July or November/December/January.