Hi Bruno
The tool is not free. If you have BO/BI license BODS is available in that package itself you can use that. Regarding customization, field mapping templates and WebI reports configuration related to BODS is available in service market place. The time taken based on the following points.
1) How you are going to use the staging SQL server 2014 or 2012 or 2016 or oracle 12c or oracle 11g
2) How many SAP source systems need to connected for migration
3) If you consolidate many SAP system into one then how to identify duplicates of Material master, Customer master and Vendor Master, G/L, Cost Center, Profit Center, Purchase Org, Sales Org etc
4) How will you handle open order like PO, SO, Planned order, Open items like AR,AP, GL etc
5) What is plan for Data cleansing strategy.
So many topics need to be consider the above are few question came to my mind.
Remember DATA MIGRATION IS NOT SIMPLY A TECHNICAL MIGRATION ITS THE PROCESS IMPROVEMENT WITH HIGH QUALITY OF DATA.
Thanks and Regards
Vijay