Terms, conditions and prices are generally negotiated on a per project basis. This page therefore only provides generic information about possible arrangements.
In general, services are provided on either an hourly or a per-project basis. Per-project contracts are generally used for smaller projects with a clearly defined scope, while larger or more abstractly specified projects are charged per hour.
Consulting hours can be pre-purchased in fixed-size packages and be called upon as needed, or be invoiced monthly. In the latter case, there is a minimum of hours that will be charged in each month where services were provided.
Payments are typically split into at least two parts, with the first part due on contract signing. 19% German VAT may apply depending on legal status and location of clients. Payment is via wire-transfer to Germany.
Prices are charged in Euro and depend on the kind of project. A substantial discount is available for work that can be delivered as open-source software.